The present invention relates to repairing for a reactor pressure vessel and structures inside the reactor pressure vessel in service, particularly a method and a device for repairing an annulus of the pressure vessel while nuclear fuel and coolant are removed.
Though safety has a priority in any devices, the safety of a reactor pressure vessel has the highest priority in a nuclear power plant, and repairing the nuclear pressure vessel and structures inside the nuclear pressure vessel during service period is prescribed.
The repairing operation for the pressure vessel is usually conducted while a repairing device is installed inside the vessel. The prior art adopts an operation procedure, in which the repairing device is inserted into the pressure vessel from the top of the nuclear reactor, and the device is taken out after the repairing operation.
During the repairing operation, usually the pressure vessel is filled with water, and remote control devices with submersible capability are used in order to reduce the exposure to nuclear radiation of operators.
Usually a chain block is used for installing the repairing device, and a method of lifting the repairing device, and inserting it into and taking it out from the pressure vessel is adopted. When the repairing device is being lift down to a baffle plate of the annulus, it is difficult to check the position of lifting down from the top of the nuclear reactor since the structures inside the nuclear reactor stand together in the course.
Also, since this is a complicated operation requiring monitoring with a submersible television camera for an interference of the repairing device, the operation takes a long period.
Here, the annulus is a space in a toric shape formed in a part surrounded by an inner wall face of the pressure vessel outside a core shroud in the pressure vessel of a boiling water reactor.
Thus, in the prior art, the situation described above is a serious problem for reducing the exposure and shortening the process.
In addition, since the remote control devices with submersible capability require a waterproof seal structure or a waterproof pipe to be installed, designing such a device is demanding, and largely increases the cost.
In addition, welding and PT (liquid penetrant flaw detection) inspection require making the inside of the pressure vessel aerial. After the repairing device is installed, reactor water is drained the for operation. After the operation, the pressure vessel is filled with water to remove the repairing device. This repeated filling/draining operation extends the operation period, and increases the operation cost.
For instance, as described in Japanese Application Patent Laid-open Publication Nos. Hei 09-159788, Hei 09-211182, and 2000-258587, devices are disclosed for allowing individual operations of inspecting, repairing, and preventively maintaining structures in the nuclear reactor such as a jet pump and an outer surface of a shroud installed in the annulus while water is filled.
In this case, since the operation is conducted under water, it has a large effect on reducing the exposure of the repairing device itself and operators when installing the device. However as described before, the operation is conducted remotely, the operation is extremely difficult, and the increase of cost is not negligible. Further, the welding and the PT inspection in the repairing operation should be aerial, and they require filling/draining water in the reactor repeatedly, resulting in a problem of the extended operation period as described before.
On the other hand, Japanese Application Patent Laid-open Publication Nos. Hei 11-174192 and Hei 11-109082, for example, disclose devices, which have access to the annulus in the water and travel automatically on the baffle plate through remote operation for nondestructive inspection. Even in this case, as described before, since the remote operation under water is assumed, the operation is extremely difficult, and if a repairing is required, these devices cannot apply to the repairing and the repairing device since the repairing should be aerial.
The prior art described before does not consider repairing applied to an annulus of a pressure vessel, and has the problem of difficult operation and extended work period.
If the prior art is applied to repairing of a reactor pressure vessel in service, installing/removing the repairing device are conducted in water, and operations such as welding and PT inspection are conducted in air.
It takes a fairly long time to drain and to fill reactor water in the pressure vessel.
Installing/removing the repairing device requires monitoring with a submersible camera for an interference of the repairing device with the structures in the reactor. Further, when the repairing device is inserted into the annulus, since it is difficult to determine the position of the repairing device, the repairing operation becomes extremely difficult.
The previous art causes the problem of difficulty in the repairing operation and the extended work period.
Also, since the repairing device should be installed/removed under water, the repairing device should have waterproof capability, resulting in a large cost in design and production.
Further, the previous art does not provide a technique for repairing from the both sides when repairing is difficult for an operation from one side of the pressure vessel.
The purpose of the present invention is to provide a method and a device for repairing the inside of a pressure vessel of a nuclear reactor, which conduct the repairing operation in an annulus of the reactor pressure vessel easily in a short period.
The purpose described before is achieved such that coolant in a reactor pressure vessel of a boiling water reactor provided with a recirculating nozzle is drained, a recirculating piping connected to said recirculating nozzle is cut to produce an opening connected to said recirculating nozzle, the repairing device is brought into said annulus in said reactor pressure vessel from said opening, and said repairing device repairs the inside of said annulus.
The purpose described before is also achieved such that coolant in a reactor pressure vessel of a boiling water reactor provided with a recirculating nozzle is drained, a recirculating piping connected to said recirculating nozzle is removed from a recirculating pump to produce an opening connected to said recirculating nozzle, the repairing device is brought into said annulus in said reactor pressure vessel from said opening, and said repairing device repairs the inside of said annulus
Simultaneously, the purpose described before is also achieved such that either inspecting a repaired part with a camera, installing monitoring cameras during repairing, detecting flaws with ultrasonic or beveling for repairing with electrical discharge machining is conducted from the top of said pressure vessel before the coolant in said reactor pressure vessel is drained.
Simultaneously, the purpose described before is also achieved such that said repairing device is brought into said reactor pressure vessel through said opening, said repairing device is lifted up/down with a jig for lifting-up/down, said repairing device is separated from said jig for lifting-up/down after it reaches the height of a baffle plate, said repairing device is mounted on said jig for lifting-up/down again after repairing the inside of the reactor, and the repairing device is recovered from the inside of the reactor.
The purpose described before is also achieved such that said jig for lifting-up/down is brought in by a straight or curved guide held by a jig for bringing-in through said opening.
This allows installing the repairing device to the annulus to be repaired without interfering with constituting devices in a nuclear reactor. Since the distance between a recirculating water outlet nozzle and the annulus is short, and the repairing device can pass while avoiding a reactor core area with high nuclear radiation, the degradation of the repairing device due to the nuclear radiation is avoided.
Also this allows traveling the repairing device in parallel from said opening to the inner wall of the reactor pressure vessel, and to travel the repairing device horizontally along the inner wall of the reactor pressure vessel from the height of said opening and to the application height for the repairing operation, thereby minimize a driving part required for the repairing device and reducing the seize of the repairing device, resulting in providing a margin for traveling of the repairing device on the annulus. This also allows inserting the repairing device into the nuclear reactor after the repairing device is aligned to the direction for the operation before hand, thereby making the travel in the reactor easily.
The purpose described before is achieved by a repairing device comprising an operation tool for repairing an inside of an annulus when coolant in a reactor pressure vessel of a boiling water reactor provided with a recirculating nozzle is drained, a recirculating piping connected to said recirculating nozzle is cut to produce an opening connected to said recirculating nozzle, the repairing device is brought into said annulus in said reactor pressure vessel from said opening, and suction disk pads for maintaining the attitude by sticking to a wall face inside said annulus.
The purpose described before is also achieved by a repairing device comprising an operation tool for repairing an inside of an annulus when coolant in a reactor pressure vessel of a boiling water reactor provided with a recirculating nozzle is drained, a recirculating piping connected to said recirculating nozzle is cut to produce an opening connected to said recirculating nozzle, the repairing device is brought into said annulus in said reactor pressure vessel from said opening, and suction disk pads and driving rollers for traveling in the horizontal direction or for turning while maintaining the attitude by sticking to a wall face inside said annulus.
Simultaneously, said repairing device may have multiple joints for freely changing the shape according to the curvature of the wall face inside said annulus, or said repairing device may be simultaneously provided with encoders so as to detect the rotations of said driving rollers and the angle of said joints, and is constituted so as to calculate at least either a position inside said reactor pressure vessel, the curvature of the inner wall face, or a distance between the nuclear pressure vessel and a jet pump diffuser.
Simultaneously, said repairing device may be simultaneously provided with double-sided suction disk pads for traveling on a discontinued and separated wall faces such as from a wall face of the reactor pressure vessel to an outer face of the jet pump diffuser.
Simultaneously, the purpose described before is also achieved such that said repairing device is provided with an operation tool driving mechanism conducting at least one type of motion of moving said operation tool up/down, rotationally, and while swinging it, said operation tool is either a welding torch, a laser head, an electric discharge machining device, a camera, a grinder, a dust collector, a device for applying liquid penetrant for detecting flaws, cleaning, and inspecting, an ultrasonic probe, or a dimension measuring device, and these tools are changed to conduct repairing such as welding, laser machining, electric discharge machining, visual inspection, polishing, grinding, collection dusts and chips, detecting flaws with liquid penetration, detecting flaws with ultrasonic, and measuring dimension.
Simultaneously, the purpose described before is also achieved such that the operation tool installed on said repairing device is a cable/hose relay box, said repairing device is brought inside the annulus after a first repairing device including the operation tool to relay cables and the hoses for the first repairing device, and said repairing device supports routing cables and hoses from the nozzle to the first repairing device.
Simultaneously, said repairing device may be constituted such that the repairing device extends arms or cushions to a wall face on the opposite side for pushing the wall face for fixing when the device is fixed on a part of a wall face where the suction with the suction disks is difficult.
Simultaneously, the purpose described before is also achieved such that said jig for bringing-in is provided with a member for shielding radiation so as to add a function for shielding radiation irradiated from the reactor pressure vessel when a operator comes close to a cut part on a recirculating piping, an outlet nozzle for recirculating water, or a safe end of the outlet nozzle for recirculating water.
Simultaneously, the purpose described before is also achieved such that said jig for bringing-in is provided with a bendable self-traveling mechanism, and is constituted so as to travel by itself to bringing in said repairing device when said repairing device is brought into the reactor pressure vessel through a bent piping from said opening.
Simultaneously, the purpose described before is also achieved such that said device for applying liquid penetrant for detecting flaws, cleaning, and inspecting has an airbag mechanism and a liquid suction nozzle, and an enclosed space is formed around a part to be repaired by pressing said airbag mechanism against the part to be repaired, thereby sucking the liquid penetrant for detecting flaws and cleaning liquid without diffusing, resulting in eliminating cleaning a wide area other than the subject part.
Simultaneously, the purpose described before is achieved such that said electric discharge machining device is provided with an airbag mechanism, a machining liquid injection nozzle, a machining liquid suction nozzle, and an electric discharge machining electrode, and an enclosed space is formed around a part to be repaired by pressing said airbag mechanism against the part to be repaired, the electric discharge electrode is pressed on a face to be machined to conduct electric discharge machining while the machining liquid is flowing from said machining liquid injection nozzle, thereby sucking machining chips without diffusing, resulting in enabling local electric discharge machining under an aerial environment without water.
Simultaneously, the purpose described before is achieved such that inspecting a part to be repaired with a camera from the top of the reactor pressure vessel and beveling for repairing with an electric discharge device brought to the part to be repaired through a guide pipe installed in water are conducted from both the annulus side and the inside of the nuclear reactor in a submersed state before coolant in the reactor pressure vessel is drained, the repairing device is brought in with said method from an opening of recirculating piping, an outlet nozzle for recirculating water, or a safe end of the outlet nozzle for recirculating water in an aerial state after coolant is drained, another repairing device is brought in the nuclear reactor through said guide pipe from the top of the reactor pressure vessel, repairing operation is conducted both from the annulus side and the inside of the nuclear reactor side, and the same part is repaired from the both sides.
With the mean described before, attaching the suction disk pads to the repairing device easily holds the repairing device at a certain position for repairing operation.
Attaching the driving rollers for traveling to the repairing device provided with the suction disk pads allows the repairing device to travel by rotating the driving rollers while the suction force is maintained, thereby traveling rotationally while maintaining the same height around the structures in the annulus, resulting in having access to a part to be repaired.
Further, since the repairing device is constituted as a symmetrical multiple joint structure and is provided with the disk pads on the both sides, when the repairing device is installed the annulus, folding said joint on one side move that side of the repairing device to a neighboring structure in the reactor, and the suction disk pad holds that side of the repairing device to said neighboring structure. Folding the joint on the other side to the structure to which the repairing device travels onto moves the entire repairing device to the neighboring structure in the reactor.
The position in the reactor and the curvature and the like of the wall face of a structure to which the repairing device sticks are obtained by detecting and calculating the rotations of the driving rollers with the encoders, thereby obtaining precise position information and shape information of the structure.
The design of the device is unified by mounting and changing the operation tools for repairing according to the purpose on said repairing device, thereby decreasing the cost for design and production, and increasing the reliability, resulting in allowing various repairing operations in the annulus.
The load on routing cables and hoses for the repairing device is eliminated when the repairing device is reaching a part far from the outlet nozzle by installing a cable/hose relay box on a second repairing device, and bringing the second repairing device into a nuclear reactor as an auxiliary carriage for handling cables, thereby reducing trouble potential caused by the cable handling, resulting in a reliable operation.
Said repairing device provided with the suction disk pads are fixed by extending arms or cushions to a direction opposite to the wall face to which the device sticks, thereby fixing the device stably on a wall face with recesses and protrusions.
The opening has a high dose rate, and is a hard environment for operators to approach since nuclear radiation from the reactor pressure vessel is irradiated from the nozzle or the opening of the piping.
Providing a shielding capability for a jig for bringing-in to shield the radiation from the opening makes the environment easy to approach.
If there is a bent part in a bringing-in path from the opening to the annulus, using self-traveling bringing-in device as a jig for bringing-in enables to bring in the repairing device to the annulus.
When liquid penetrant flaw detecting inspection is conducted, installing airbag mechanism and a liquid suction nozzle to a liquid penetrant flaw detecting device enables to press the airbags to a part to be repaired to form an enclosed space, thereby sucking liquid penetrant for detecting flaws and cleaning liquid without diffusing, resulting in eliminating cleaning a wide area other than the subject part.
For an electric discharge machining for eliminating flaws and beveling for repair, an electric discharge machining device is provided with an airbag mechanism, a machining liquid injection nozzle, and a machining liquid suction nozzle and an enclosed space is formed by pressing said airbag mechanism against the part to be repaired, and electric discharge machining is conducted in said enclosed space thereby sucking machining chips and the machining liquid without diffusing, resulting in local electric discharge machining under an aerial environment without water while maintaining the surrounded area clean.
For a method inspecting a part to be repaired and removing flaws, inspecting and repairing simultaneously or alternately from the annulus side and the inside of the reactor effectively applies a highly reliable inspection and repair to a wide area.